This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Like lymphoid organs, the CNS is an important tissue reservoir for HIV. HIV-related neurological conditions, including HIV-associated dementia, are known to occur as a result of viral replication and persistence in the CNS of HIV-infected individuals. Highly active antiretroviral therapy (HAART) has reduced the incidence of HIV dementia as well as most of the other neurological complications of AIDS, presumably by suppressing viral replication in nervous tissues. However, it has been difficult to measure the effect of antiretroviral treatment on viral load in brain tissue directly, as well as the impact of HAART on the outcome of encephalitic lesions in the CNS of HIV positive patients, because brain tissue is not readily accessible for analysis. We are using the CD8-depletion model of SIV encephalitis (SIVE) in rhesus monkeys to directly measure the impact of combination antiretroviral therapy (CART) on brain virus burden.